Head space micrometer gauge



Sept. 27, 1949. H. P. FERGUSON 2,483,089

HEASPACE MICROMETER GAUGE Filed July 22, 1948 IN V EN TOR.

\ Hiram l? Fguson Patented Sept. 27, 1949 My invention pertains Ito micrometer's`,-and Vrelates `particularly to.a micrometer gaugeA constructed inthe shape-of a cartridge for measuringthe headspace of cartridge chambers in'frearmsj-.l..r= re' YI, ,j 1: .A .principalobject ofrrmyinvention is the provision ofamicrome'ter gauge which is constructed ini the shapeoff Sa cartridge, wherebyv said gauge may be workedinto and out of the cartridge chamber .fby 'means of :the:` mechanism provided in-the.l.rearm. v :A A Another object Vis.!toproviide a 4micrometer gauge which may` be Sfplaced inthecartridge chamber of --a firearm Vfor measuring fthe headspaceof saidichamber without removing. the flring' pinf'f'or otherwise insuring against accidental damage-ofith'lattenY. .-4 f furtherobject iisfthepr'ovision --in a headspacel micrometer-gauge Yof 'adjustablel -meansfo'r locking said gauge at anyselected reading: 'l

still further object is :to provide'anradjustable micrometer gauge for measuring the headspace in thefoartridge-chamber of -thelrifla said measurement being determined by the -feel of hand pressure required to close theboltfV v These and other objectsfrand advantages-of 'my invention will appear: from the following detailed description .taken in connectionwith the-accompanying drawing, inwhich'r,y e 1.is1a fragmentarysectional*y view-ict the operating mechanism of a rifle,y showing a headspace micrometer gauge. ,embodying my inven-l tion-'J arranged;inthel cartridge chambenot said riile for imeasuring; lthe? headspace thereof; m 1 Y. i Fig. 2.is'aAplan-viewrof.the headspace microm-r eter'shown in Fig. 1"Withpartslthereoffshown brokenawayfto disclose details of construction.; i' Figr .is'antend-View of. the headspace'micrometer shown`in Fig: 2 vas.vie\7ved in-th'etdirec-` tion of arrows 3'3 in Fig; 2;:and E,

Figni is a sectional view of the lieadspace mi` crometer '.taken. alongf-.the lines-4rd; ini-:Ei'g-.i2l

Referring Yparticularly .to Fig. 2 whereiniaf'micrometerI gaugefembodying'my invention is'illustrated Iindetal; saidjgaug'e comprisesdzhre'e parts, viz., '.abarrelI, a mierometerscreW'Zrand arr-ad.- justment -:screwf 3ra 1 Complementaryrfthreads formed ini the'icooperating 4parts-;:renovablytj oin thea-latter. ini-operative relationp as sisfinore .fully described hereinafter); 5.a c V; LA. f Theibarrel: If:` comprises.'v a manovre-cylindrical tube. ,One end of said barret is of `.larger outside diameter -`than=thezremainingi portion, said enlarged sectionfrbeingesubstantially the same diam# eter iasithreawaxzdiend Qi-theicartridge cham-1 'tv olaims. write-153) toameasure ber- `Lforxr'iedin the gumbarrel 53. Agroove .6 extends.circumferentially around said enlarged sectionftol-dene-*a simulated-rim to be engaged bythe ejector vmechanism ofthe rie. The gauge may thus bef-readily withdrawn from the chamber-4 vin the same manner as-cartridges are ejected thereflromw- 'Ihe opposite end- 1-of the barrel. Il istaperedglforconvenience, and-unit graduations -'are marked-about .the circumference thereof. Although AILhave` shown-the section of the` barrel -I intermediate-the enlarged end'and `tapered to begaf-reduced diameter, itis understood that the outsidediameter of1 said barrel .may conform throughout itsfentirelength to the diameter of the cartridge -chainber.4, 5. i i @The central-- Abore `extending ilongitudinally through! saidbarrel Ikis providedwith. internal threads 9 disposed intrmediatetheends of said bore throughouta substantialV bportion of its length. 'SaidV bore .is 'proportioned and arranged to`receivelan end 'section 2d of the micrometer scew'the'rin. The external threads I0 formed about-'said exi'd sectionv 2a engage internalthreads 9 of the'barrel YI; Inthis manner the barrel and micrometer screw'are removably'and'adjustably joined 'togetherto form the main body of the ga'gl'f" 'i The'end ofsaidimicrometer screw opposite the threads w i's of reduced diameter and pointed at"itseitreinit'y,fformingl a nose y:section I #which projctsbeyon'd the'chamber-l into the bore vI2 of `-'the""gun barrel 5.- It is apparent that said nose tsction"simulates the projectile element of ar'c'artrid'g: VAn enlargedfsection' I3 is-formed circumferentiallyabout-the micrometer screw adja'cent" the nose=section II. .Said enlargedY sectiohfl:ias--=al adiam'eter substantially equal to .the diameter Eoffthe `forward end -of the. cartridge chamberL-'aridris -tapered toward the nose section to: form-"a shoulder; Mu Said shoulder conformswto;theftaperiof thea-forward :end -of the cartridgechamberiwith whichit comesfinto close contact when the gauge is positioiqied-in vthe chambr'l' I.' Il lf2. '7* lz-The lsection:ofL-the micrometer screw a2 between the.;fthreadsffillfxand; enlarged 'sectQIrv I3 Vis vprovided with suitah1e-graduati0ne l5 marked at unit intervals along the) longitudinal, dimension cfcsaidfsecton-i The 'gallifipns 3L are arranged raetional distances? between each graguatlo. ralf-exemple with threads. "l ier-med 'fevrtyeto th inclnthe distance. between, h l. 1llti?.! .I .fhh measlllffon lfm/0111" .tiontoLf-theiharrel. L with riespetztqtlie micrometerasrerr 3, iiiyeoeiuqlli; Pili-teil flYSi graduation marks 8 arranged circumferentially about the end 1 of the barrel will provide for reading the micrometer to the nearest 0.001 inch. One of the intermediate graduations I is designated as zero, i. e. with the barrel end 1 set at said Zero mark the distance between the end adjacent the groove and the end of shoulder I4 is equal to the standard length of that portion of a cartridge which lies between the end of the rilie bolt I8 and the tapered forward end ofk the cartridge chamber 4. The graduations on either side of the zero mark indicate the amount, plus or minus, by which the headspace of the chamber I 4 deviates from standard or optimum. y

The threaded end of the micrometer4 screw `i. is provided with a longitudinal bore. Threads 'barrel t..

4 gauge in fixed position, the latter is again inserted in the chamber 4. This procedure is repeated until the proper hand pressure for closing the bolt is obtained. The reading of the gauge may then be compared with the standard tolerance allowed for the rifle to determine whether the gun may be used with safety. Y

It is to be noted that the gauge embodying my invention may be used without the necessity of rst removing; the firing pin.l Incase the trigger is released accidentallyY while the' gauge is positioned in the cartridge chamber, the firing pin will project forwardly into the central bore of the The micrometer screw 2 cannot be threaded into the barrel to a depth sufficient to cause the tiring pin to strike the end of the ad- I'I are formed in said bore and extend outwardly' 1; toward the end of the screw 2. The section I8- Y between the threads I'I and the end of thefscrew is tapered outwardly from said threads. Longitudinal slits I9 are formed` at spaced intervals about the circumference off said tapered section and extend longitudinallyof said screwY 2;. The adjustment screw: 3 is` threaded for-a substantial portion of its length,4 saidthreads` beingr constructedto engage the internal threads I'Tformed in the bore ot; the micrometer screw. The remaining unthreadedx length of'. the adjustment screw tapers' outwardly toward its end to form a head which engages. the tapered section I8.

A screwdriver slot provided at the end of' said head a-lords means for turning the adjustment screw. As the screw is. moved-inwardly of the bore, the tapered head spreadsy the sections i8 radially outward in tighter'engagement with the barrel l. The increased friction between the threads 9 and MI resulting from said tightening eect increases the force necessary to cause relative rotation between the barrel I Aand micrometer screw 2. The screw 3 may bel adjustedto any desired position, and may be set in such manner aseftectively to lock the barrel and micrometer screw in fixed relation with` each other. It-isto be noted that the slot 20 is accessible through the boreprovided in the barrel i.' Thus, the micrometer gauge may be rotated to a selected position and then locked by turning the screw 3 until the parts are secured against subsequent rotation.V

In the use of the gauge formeasuring the headspace of a rifle', the gauge is insertedin the cartridge chamber 4 to. the position shown in Fig. l of the drawing. Since the 'gauge'is constructed in the shape of the cartridge designed for the particular rifle', the loading mechanism ofthe latter may be employed for inserting the gauge. Alternatively, the gauge may be positioned in the chamber by hand, if desired. It is recommended that the gauge be set initially to standard or optimum length, i. e. to the zero marking of graduations 8 and I5. With the shoulder 'I4 in firm contact with the tapered end of the chamber 4, the bolt i6 is moved forward against the enlarged end of the barrel I.

By observing the amount of hand pressure required to close the bolt, the operator is Aable to determine the headspace of the cartridge chamber. For example, if the bolt appears to close easily and without striking the end of the barrel I, the bolt is retracted and the gauge is removed from the chamber by means of the ejector mechanism.' Since the rst test indicated the headspace to be greater than standard, the gauge is manipulated in such manner as to lengthen the distance between the end of the barrel I and the-shoulder M. After setting the Vadjustmentv screw 3 to lock'the jjustment. screw- 3.; In this manner possible damage to the firing pin is eliminated, and the headspace of the cartridge chamber may be measured while the rifle is in fully` assembled condition.

I claim: l i Y l., A micrometer gauge for measuring the head- Space of the cartridge chamber ofiirearms, comprisme a circlimier-.entiall-yl calibrated barrel having a threaded axial bore and at least a portion of its; outside: diameter: being; substari-ti'allyV the same as. the diameterV of the: cartridge; chamber of said firearm, means adjacent one end of said barreI for accomodating the ejector mechanism of said firearm, a i nicronicterA Screw having an enlarged intermediate section tapered in conformity With the tapered end of said cartridge chamber, said enlarged section having; a diameter substantially the saine as the diameter of said chamber, one end 0f said miometer screw being of reduced diameter and receivable; the barrel boreofsaid iirearm, the opposite endy of said micrometer screw having vexternal threads formed thereon proportioned and arranged to engage the threaded bore off said micrometer barrel for longitudinal movement; relative thereto, and longitudinal calibrations on` said. micrometer'screw registering with thecaligbrationson said barrel.

2. A-micrometer gauge for measuring the headspace of the; cartridge chamberof rearms, comprising a barret a threaded' axial bore and an Outside diameter' substantially the same as the diameter of the cartridge chamber of said firearm, a circumferential groove adjacent one end of said barrel for acvriornmodating the ejector mechanism of said firearms, circumferential calibrations on.- the opposite` end or said barrel, a micrometer screw-havinganenlarged section tapered in conformity* with the tapered endof said cartridge chamber.. Said enlargedy sectionhaving a diameter substantially the 'samej as the diameter of said chamber',A one,` end of said micrometer screw having external threads formed thereon proportioned and arrangedv to engage the threaded bore of said micrometer barrel'for longitudinal movement relative thereto, and longitudinal calibrations on said micrometer screw registering with the calibrations on said barrel.

3. A micrometer gauge for measuring the headspace of the cartridge chamber of firearms, comprising a cireumf'erentially calibratedbarr'el having a threaded axiai bore and at least a-portion ofits'outsid'e diameterwbeing substantially the saine as the diameter of the cartridge chamber of said firearm, means adjacent one end or said barrel for accommodating'the ejector mechanism ofsaid ilrearm, ai micrometerscrew having an enlarged section tapered' in conformity with the tapered end of said cartridge chambensaid enlarged section having a vdiameter substantially the same as the diameter of said chamber, one end of said micrometer screw having external threads formed thereon proportioned and arranged to engage the threaded bore of said micrometer barrel, longitudinal calibrations on said micrometer screw registering with the calibrations on said barrel, the threaded end of said micrometer screw being slotted longitudinally and having an axial bore therein, and a tapered adjustment screw threaded in the axial bore of said micrometer screw for adjustably securing the micrometer barrel and screw together in selected position.

4. A micrometer gauge for measuring the headspace of the cartridge chamber of rearms, comprising a circumferentially calibrated barrel having a threaded axial bore, a micrometer screw having external threads formed thereon proportioned and arranged to engage the threaded bore of said micrometer barrel for longitudinal movement relative thereto, longitudinal calibrations on said micrometer screw registering with the calibrations on said barrel, the threaded end of said micrometer screw being slotted longitudinally having an axial bore therein, a portion of said bore being tapered outwardly toward the end of said micrometer screw, the remaining portion of said bore being threaded, and a tapered adjustment screw threaded in the axial bore of said micrometer screw for adjustably securing the micrometer barrel and screw together in selected positions, said gauge having the shape of the cartridge designed for said firearm.

5. A micrometer gauge for measuring the headspace of the cartridge chamber of firearms, comprising a barrel having a threaded axial bore and at least a portion of its outside diameter substantially the same as the diameter of the cartridge chamber of said firearm, means adjacent one end of said barrel for accommodating the ejector mechanism of said rearm, circumferential calibrations on said barrel, a micrometer screw having an enlargedintermediate section tapered in conformity with the tapered end of said cartridge chamber, said enlarged section having a diameter substantially the same as the diameter of said chamber, one end of said micrometer screw being receivable in the barrel bore of said rearm, the opposite end of said micrometer screw having external threads formed thereon proportioned and arranged to engage the threaded bore of said micrometer barrel, longitudinal calibrations on said micrometer screw registering with the calibrations on said barrel, the threaded end of said micrometer screw being slotted longitudinally and having an axial bore therein, and a tapered adjustment screw threaded in the axial bore of said micrometer screw for adjustably securing the micrometer barrel and screw together in selected positions.

HIRAM P. FERGUSON.

REFERENCES CITED UNITED STATES PATENTS Name Date Eickhoff et al Aug. 31, 1920 Number 

